Thank you for the advice. and, I'm very sorry. the connection and sketch I indicated was wrong. confused. Finally I reffer and correct information are here. Maybe, it is almost dead copy of the refference page. https://lang-ship.com/blog/work/m5stickc-spi-sd-3wire/ M5StickCPlus >>>> SD 3V3 >>>> 3V3 GND >>>> GND 0 >>>> CLK 36 >>>> MISO 26 >>>> MOSI GND >>>> CS #include <M5StickCPlus.h> #include "SD.h" SPIClass SPI_EXT; // PIN配置 enum { spi_sck = 0, spi_miso = 36, spi_mosi = 26, spi_ss = -1 }; void setup() { // M5StickC initialize M5.begin(); M5.Lcd.setRotation(3); // SPI initialize SPI_EXT.begin(spi_sck, spi_miso, spi_mosi, spi_ss); // SD initialize if (!SD.begin(spi_ss, SPI_EXT)) { M5.Lcd.println("Card Mount Failed"); return; } // SD check uint8_t cardType = SD.cardType(); if (cardType == CARD_NONE) { M5.Lcd.println("None SD Card"); return; } M5.Lcd.print("SD Card Type: "); if (cardType == CARD_MMC) { M5.Lcd.println("MMC"); } else if (cardType == CARD_SD) { M5.Lcd.println("SDSC"); } else if (cardType == CARD_SDHC) { M5.Lcd.println("SDHC"); } else { M5.Lcd.println("UNKNOWN"); } // SD volume uint64_t cardSize = SD.cardSize() / (1024 * 1024); M5.Lcd.printf("SD Card Size: %lluMB\n", cardSize); } void loop() { }